1. Field of the Invention
The present invention relates to a power amplifier which may have a compensation function for compensating an output phase fluctuation (AM-PM) caused in accordance with the fluctuation of an input level.
2. Description of the Related Art
In recent years, mobile communications terminals have come into widespread usage due to the ease of use thereof. With an increase in the use of mobile communications terminals, extending a use period thereof has become a high priority, together with a variety of application activations, so as to provide consumer satisfaction.
In order to increase a mobile communications terminal usage period, it is important to increase the capacity of the battery thereof; however, there are limitations in extending battery life, in that market conditions requiring reductions in the weight, thickness, length, and overall size of a mobile communications terminal indicate that battery size cannot be easily increased. Accordingly, it is necessary to increase the power efficiency of important internal components of mobile communications terminals.
In addition, power amplifiers for transmitting and receiving radio signals are used in the mobile communications terminals. Power amplifiers account for a significant portion of the total power consumption of mobile communication terminals, such that the power efficiency thereof is required to be increased.
Meanwhile, the power amplifier is generally manufactured to include a compound semiconductor; however, a proportion of power amplifiers manufactured using a CMOS (Complementary Metal Oxide Semiconductor) process has gradually increased, due to an increase in the manufacturing costs in the case of the manufacture using a compound semiconductor and an increase in the technological development of the CMOS process and associated circuit design.
Power amplifiers are required in order to satisfy device linearity characteristics required by consumers; however, they are designed so as to satisfy linearity characteristics at a maximum output level, due to a trade-off between power consumption and linearity.
As a method for satisfying linearity characteristics, a method that suppresses fluctuations in the level (AM-AM) of output signals in accordance with a level fluctuation of input signals has mainly been used. However, even in this method, fluctuations in the phase (AM-PM) of the output signal may occur in accordance with the fluctuations in the level of the input signals, such that linearity characteristics may not be satisfied.